Method and apparatus for melting and casting metal

Abstract

A method of melting and casting metal comprising the steps of melting metal in a melting vessel, transferring metal from the melting vessel into a casting vessel by flow of metal under gravity and pumping metal against gravity from the casting vessel into a mold. The level of the top surface of the metal as the metal leaves the melting vessel is above the top surface of the metal in the casting vessel by not more than a maximum distance above which excessive turbulence occurs. The maximum distance lies in the range 50-200 mm.

I claim: 
     
       1. A method of melting and casting metal comprising the steps of melting metal in a melting vessel, advancing a quiescent flow of said molten metal, by gravity, along the whole of a path from said melting vessel into a casting vessel to provide a reservoir of molten metal which dwells in said casting vessel, said path being defined to maintain the level of the top surface of the metal as the metal leaves the melting vessel above the top surface of the metal in the casting vessel by not more than a distance of 200 mm and sequentially pumping a discrete volume of said molten metal against gravity from the casting vessel into each of a plurality of individual moulds. 
     
     
       2. A method as claimed in claim 1 wherein said distance is in the range 100-50 mm. 
     
     
       3. A method as claimed in claim 1 wherein the method includes the steps of directing metal from the melting vessel into a launder and from the launder into the casting vessel, the launder being disposed to maintain the level of metal in the launder at a level which is below the level of the top surface of the metal as it leaves the melting vessel and is at or above the level of the top surface of the metal in the casting vessel. 
     
     
       4. A method as claimed in claim 1 wherein said distance is substantially zero. 
     
     
       5. A method as claimed in claim 4 wherein metal is added to the melting vessel at substantially the same rate as metal is pumped from the casting vessel. 
     
     
       6. An apparatus for melting and casting metal comprising a melting vessel, a casting vessel, means defining a path for quiescent flow of molten metal under gravity and along the whole of the path from said melting vessel to said casting vessel so that the level of the top surface of said molten metal as said molten metal leaves said melting vessel is above the top surface of the molten metal in said casting vessel by not more than a distance of 200 mm and a pump to pump sequentially a discrete volume of metal against gravity from the casting vessel into each of a plurality of individual moulds. 
     
     
       7. An apparatus as claimed in claim 6 wherein said distance is substantially zero. 
     
     
       8. An apparatus as claimed in claim 6 wherein the apparatus includes a launder having an entry end located so that metal leaving the melting vessel may enter the launder thereat and an exit end whereby the metal may flow from the launder to the casting vessel, the launder being disposed to maintain the level of the top surface of the metal in the launder at a level which is below the level of the top surface of the metal as it leaves the melting vessel and is at or above the level of the top surface of the metal in the casting vessel. 
     
     
       9. An apparatus as claimed in claim 6 wherein the melting vessel comprises a lip action tilting vessel. 
     
     
       10. An apparatus as claimed in claim 6 wherein the casting vessel and the melting vessel are provided by different, intercommunicating, regions of a common vessel so that said distance is substantially zero. 
     
     
       11. An apparatus as claimed in claim 6 wherein filter means are incorporated in the metal flow path from the melting furnace to the casting vessel. 
     
     
       12. A method as claimed in claim 1 wherein the metal is an aluminium alloy lying in the following composition range:   ______________________________________                                    
Si         10.0     11.5                                                  
Cu         2.5      4.0                                                   
Mg         0.3      0.6                                                   
Fe         0        0.8                                                   
Mn         0        0.4                                                   
Ni         0        0.3                                                   
Zn         0        3.0                                                   
Pb         0        0.2                                                   
Sn         0        0.1                                                   
Ti         0         0.08                                                 
Cr         0         0.05                                                 
Usual      0         0.09     (each incidental)                           
Incidentals                                                               
Aluminium  Balance.                                                       
______________________________________                                    
     
     
     
       13. A method as claimed in claim 12 wherein the silicon, copper and magnesium contents are as follows:   ______________________________________                                    
Si              10.5   11.5                                               
Cu              2.5    3.5                                                
Mg              0.3    0.5                                                
______________________________________                                    
     
     
     
       14. A method as claimed in claim 1 wherein the mould is made of chemically bonded zircon sand.